fbsetroot: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/bin/fbsetroot - from package: fluxbox

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/fbsetroot - from package: fluxbox

You may install the required package with command apt-get install {package}

Error in other languages:
fbsetroot: bevel nie gevind nie
fbsetroot: comandă negăsită
fbsetroot: comando não encontrado
fbsetroot: commande introuvable
fbsetroot: command not found
fbsetroot: käsku ei ole
fbsetroot: không tìm thấy lệnh
fbsetroot: komanda nerasta
fbsetroot: Kommando nicht gefunden.
fbsetroot: kommandot finns inte
fbsetroot: komut yok
fbsetroot: nie znaleziono polecenia
fbsetroot: níor aimsíodh an t-ordú
fbsetroot: no se encontró la orden
fbsetroot: no s'ha trobat l'ordre
fbsetroot: opdracht niet gevonden
fbsetroot: parancs nem található
fbsetroot: perintah tidak ditemukan
fbsetroot: príkaz nenájdený
fbsetroot: příkaz nenalezen
fbsetroot: команда не найдена
fbsetroot: командата не е открита
fbsetroot: 命令找不到
fbsetroot: コマンドが見つかりません